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Proportional Navigation
For example, if the line of sight rotates slowly from north to east, the missile should turn to the right by a certain factor faster than the LOS-rate. This factor is ''N''. Proportional navigation (also known as PN or Pro-Nav) is a guidance law (analogous to proportional control) used in some form or another by most homing air target missiles. It is based on the fact that two vehicles are on a collision course when their direct line-of-sight does not change direction as the range closes. PN dictates that the missile velocity vector should rotate at a rate proportional to the rotation rate of the line of sight (Line-Of-Sight rate or LOS-rate), and in the same direction. For example, if the target is seen moving from the left to the front, thus moving to the right as seen from the missile, then the missile should turn to the right until this angular motion stops again. A rather simple hardware implementation of this guidance law can be found in early AIM-9 Sidewinder missiles. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
AIM-9 Sidewinder
The AIM-9 Sidewinder is a short-range air-to-air missile. Entering service with the United States Navy in 1956 and the Air Force in 1964, the AIM-9 is one of the oldest, cheapest, and most successful air-to-air missiles. Its latest variants remain standard equipment in most Western-aligned air forces. The Soviet K-13 (AA-2 "Atoll"), a reverse-engineered copy of the AIM-9B, was also widely adopted. Low-level development started in the late 1940s, emerging in the early 1950s as a guidance system for the modular Zuni rocket. This modularity allowed for the introduction of newer seekers and rocket motors, including the AIM-9C variant, which used semi-active radar homing and served as the basis of the AGM-122 Sidearm anti-radar missile. Due to the Sidewinder's infrared guidance system, the brevity code " Fox two" is used when firing the AIM-9. Originally a tail-chasing system, early models saw extensive use during the Vietnam War, but had a low success rate (8% hit rate with th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Navigation Constant Illustration
Navigation is a field of study that focuses on the process of monitoring and controlling the motion, movement of a craft or vehicle from one place to another.Bowditch, 2003:799. The field of navigation includes four general categories: land navigation, marine navigation, air navigation, aeronautic navigation, and space navigation. It is also the term of art used for the specialized knowledge used by navigators to perform navigation tasks. All navigational techniques involve locating the navigator's Position (geometry), position compared to known locations or patterns. Navigation, in a broader sense, can refer to any skill or study that involves the determination of position and Relative direction, direction. In this sense, navigation includes orienteering and pedestrian navigation. For marine navigation, this involves the safe movement of ships, boats and other nautical craft either on or underneath the water using positions from navigation equipment with appropriate nautical char ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
International Regulations For Preventing Collisions At Sea
The International Regulations for Preventing Collisions at Sea 1972, also known as ''Collision Regulations'' (''COLREGs''), are published by the International Maritime Organization (IMO) and set out, among other things, the "rules of the road" or navigation rules to be followed by ships and other vessels at sea to prevent collisions between two or more vessels.''Convention on the International Regulations for Preventing Collisions at Sea, 1972 (COLREGs)'' , from the IMO (The International Maritime Organisation). Retrieved 13 February 2006. COLREGs can also refer to the specific political line that divides [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Motion Camouflage
Motion camouflage is camouflage which provides a degree of concealment for a moving object, given that motion makes objects easy to detect however well their coloration matches their background or breaks up their outlines. The principal form of motion camouflage, and the type generally meant by the term, involves an attacker's mimicking the optic flow of the background as seen by its target. This enables the attacker to approach the target while appearing to remain stationary from the target's perspective, unlike in classical pursuit (where the attacker moves straight towards the target at all times, and often appears to the target to move sideways). The attacker chooses its flight path so as to remain on the line between the target and some landmark point. The target therefore does not see the attacker move from the landmark point. The only visible evidence that the attacker is moving is its looming, the change in size as the attacker approaches. Camouflage is sometimes fa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pursuit Guidance
Pursuit guidance, or a pursuit course, is a form of guidance widely used in older guided missiles. In pursuit guidance, the missile is steered so that the velocity vector of the missile always points at the target, i.e. it has always the direction of the line of sight. This was the natural outcome of many guidance systems, notably beam riding systems where the missile followed the radar signal that was illuminating the target. As the radar typically used conical scanning in order to keep itself pointed at the target (radar lock-on), and the missile guided itself by centering itself in this beam, this caused it to always fly directly at the target. It was also found in early laser-guided bombs with the aerodynamically stabilized seeker/guidance ("birdy") on the front of the bomb. The birdies sit on a universal joint and thus will point in the direction of the relative wind. If the laser receiver is placed on this wind stabilized reference, the angle that the laser is off the wind ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Motion Camouflage
Motion camouflage is camouflage which provides a degree of concealment for a moving object, given that motion makes objects easy to detect however well their coloration matches their background or breaks up their outlines. The principal form of motion camouflage, and the type generally meant by the term, involves an attacker's mimicking the optic flow of the background as seen by its target. This enables the attacker to approach the target while appearing to remain stationary from the target's perspective, unlike in classical pursuit (where the attacker moves straight towards the target at all times, and often appears to the target to move sideways). The attacker chooses its flight path so as to remain on the line between the target and some landmark point. The target therefore does not see the attacker move from the landmark point. The only visible evidence that the attacker is moving is its looming, the change in size as the attacker approaches. Camouflage is sometimes fa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coenosia Attenuata
''Coenosia attenuata'' (also sometimes cited as ''Coenosia attenuate''), commonly called "hunter fly" or well known under the name "killer fly", is a predatory fly belonging to the family Muscidae. Distribution This species is native to Southern Europe, where it is present in Spain, France, Italy, Germany and Greece. It has now a worldwide distribution and it can also be found in the Afrotropical realm, in the Australasian realm, in the East Palearctic realm, in the Near East, in the Nearctic realm, in the Neotropical realm, in North Africa and in the Oriental realm. It was first discovered in the United States in 2001 by an Integrated Pest Management scout in a greenhouse in New York State. It has since been found throughout North and South America. Description Adults of ''Coenosia attenuata'' can reach a length of . These tiny killer flies have a pale brownish or greyish body, with big reddish eyes. Antennae and legs are yellow in males. Females have brownish frons, with a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Holcocephala Fusca
''Holcocephala fusca'', the gnat ogre, is a species of robber fly in the family Asilidae The Asilidae are the robber fly family, also called assassin flies. They are powerfully built, bristly flies with a short, stout proboscis enclosing the sharp, sucking Insect mouthparts#Hypopharynx, hypopharynx. The name "robber flies" reflects t .... References External links * Asilidae Articles created by Qbugbot Insects described in 1951 {{Asilidae-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optimal Control Theory
Mathematical optimization (alternatively spelled ''optimisation'') or mathematical programming is the selection of a best element, with regard to some criteria, from some set of available alternatives. It is generally divided into two subfields: discrete optimization and continuous optimization. Optimization problems arise in all quantitative disciplines from computer science and engineering to operations research and economics, and the development of solution methods has been of interest in mathematics for centuries. In the more general approach, an optimization problem consists of maximizing or minimizing a real function by systematically choosing input values from within an allowed set and computing the value of the function. The generalization of optimization theory and techniques to other formulations constitutes a large area of applied mathematics. Optimization problems Optimization problems can be divided into two categories, depending on whether the variables ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Angular Velocity
In physics, angular velocity (symbol or \vec, the lowercase Greek letter omega), also known as the angular frequency vector,(UP1) is a pseudovector representation of how the angular position or orientation of an object changes with time, i.e. how quickly an object rotates (spins or revolves) around an axis of rotation and how fast the axis itself changes direction. The magnitude of the pseudovector, \omega=\, \boldsymbol\, , represents the '' angular speed'' (or ''angular frequency''), the angular rate at which the object rotates (spins or revolves). The pseudovector direction \hat\boldsymbol=\boldsymbol/\omega is normal to the instantaneous plane of rotation or angular displacement. There are two types of angular velocity: * Orbital angular velocity refers to how fast a point object revolves about a fixed origin, i.e. the time rate of change of its angular position relative to the origin. * Spin angular velocity refers to how fast a rigid body rotates around a f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Voltage
Voltage, also known as (electrical) potential difference, electric pressure, or electric tension, is the difference in electric potential between two points. In a Electrostatics, static electric field, it corresponds to the Work (electrical), work needed per unit of Electric charge, charge to move a positive Test particle#Electrostatics, test charge from the first point to the second point. In the SI unit, International System of Units (SI), the SI derived unit, derived unit for voltage is the ''volt'' (''V''). The voltage between points can be caused by the build-up of electric charge (e.g., a capacitor), and from an electromotive force (e.g., electromagnetic induction in a Electric generator, generator). On a macroscopic scale, a potential difference can be caused by electrochemical processes (e.g., cells and batteries), the pressure-induced piezoelectric effect, and the thermoelectric effect. Since it is the difference in electric potential, it is a physical Scalar (physics ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Constant Bearing Decreasing Range
Constant bearing, decreasing range (CBDR) is a term in navigation which means that some object, usually another ship viewed from the deck or bridge of one's own ship, is getting closer but maintaining the same absolute bearing. If this continues, the objects will collide. Risk Sailors, especially deck hands and those who stand watch on the bridge, are trained to watch for this situation and make it known when they detect it happening. The reasoning is subtle: non-sailors who are used to driving automobiles normally are able to detect the possible risk of a collision with implicit reference to the background (e.g., the street, the scenery, the landscape, etc.) At sea, when vessels are borne in water, the sea surface removes this vital visual clue. Unaware individuals tend to gauge the risk of two vessels colliding based on which direction each vessel is heading. In other words, a novice will think that two vessels which appear to be heading apart from each other cannot collid ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
